1. Technical Field
The present invention relates to a technique for displaying video images on the basis of video image data.
2. Related Art
In a video image display device such as projectors, there have been proposed techniques for performing a luminance range expansion process for expanding a luminance range of image data in one frame of video image data, thereby improving a sense of contrast of the image.
In addition, in a video image display device such as projectors equipped with an illumination device, there have been proposed techniques for performing a lighting control process for adjusting the luminance of the image, thereby improving image quality. Examples of the related art include JP-A-2001-343957, JP-A-2004-45634 and Japanese Patent No. 3308234.
However, according to the luminance range expansion process known in the art, since the luminance range expansion process is performed to the video image data without consideration of an abrupt change of the image (i.e., luminance of the image) between frames, there is a possibility that the image quality is deteriorated by the luminance range expansion process. For example, at the time of a scene-change in the video image, there are cases where a previous scene fades out into a black screen and a next scene fades in from the black screen. In this case, an expansion rate of the luminance may increase in a period until the next scene fades in from the black screen. When the luminance expansion rate increases, the video image data of the next scene is excessively expanded. Therefore, there is a possibility of causing deterioration of the image quality known as halation.
The abrupt image change between frames will be referred to as a scene-change.
Moreover, according to the lighting control process known in the art, since the lighting control process is performed without consideration of the scene-change, there is a possibility that the lighting control process deteriorates the image quality.